Thermostat device controlling the correct position of a source of radiation, especially of the arc of an arc lamp



THERMOSTAT DEVICE CONTROLLING THE CORRECT POSITION OF A SOURCE OFRADIATION, ESPECIALLY OF THE ARC OF AN ARC LAMP Filed Jan. 18, 1953Sept. 29, 1936. c mz 2,055,705

Inventor: 6M @v'wh.

Patented Sept. 29, 1936 x THERMOSTAT DEVICE CONTROLLING THE CORRECTPOSITION OF A SOURCE OF RADIATION, ESPECIALLY OF THE ARC OF ANARC CarlPrinl, Jena, Germany, assignor to firm Carl Zeiss, Jena, GermanyApplication January 18, 1933, Serial No. 652,408 In Germany January 22,1932 1 Claim.

Application has been filed in Germany, January The invention concernsdevices controlling the correct position of a source of radiation,especially the are oi arc lamps, which is iable to wander on account ofthe consumption of the electrodes, the device being used to make thelight arc remain permanently, for instance, at the focus of a reflector.this kind generally contain two elements sensitive to radiation, in mostcases bimetallic strips, whichare parallel, and an optical systemimaging the source or radiation on the one element, the other elementcompensating for the effect of 5 the temperature in the surroundingspace on the first said element. Through the agency of electric contactsor the like, the sensitive elements act upon driving mechanisms, whichbring the wandered source of radiation back into its original position.

According to the invention use is made of the known device in which thebimetallic strips are parallel, this device being, however, soconstructed that the elements lie next to each other in that directionin which the image of the source of light is being displaced when thesource of light is moving in a predetermined manner, the two stripshaving such positions that, when the source of radiation assumes itscorrect position, the image so of the source of radiation projected bythe said optical system is uniformly divided over the two strips. Thisconstruction has proved and ensured a considerably better and more rapidworking of the control device than could be obtained as so far, theimprovement being due to the fact that as soon as the source ofradiation is removed from the prescribed position and the image or thissource of radiation leaves its position symmetrical to the bimetallicvstrips, the one strip is heated 40 more strongly and the other cooleddown, as a consequence-oi which the sensitivity of the device is twiceas great as that oi the devices in use hitherto, in which only the onestrip is exposed to, and the other protected from, the

45 radiation.

Itisadvisabletoso disposethesestripsinthe device that the directions oftheir breadths are inclined relatively to the direction of radiation, soas to ensure a sumcient part of their breadth 50 being influenced.

In the accompanying drawing, which illustrates the invention, Figure 1represents in'elevation'a constructional example for use in an arc lamp,Figm'e 2 a lateral section, Figure 3 a plan 55 view oi the device, andFigure 3a a side view from the upper part of Figure 3. vFigures 4 and 5show an alternative form of the said example in elevation and a planview respectively.

Inthedevicerepresentedbyl'igures 1to3a,the

The known devices of elements sensitive to radiation are two bimetallicstrips 0 and b whose one ends are fixed to a support c of insulatingmaterial resting on a base plate d. At its free end, the strip a isprovided with a contact piece ewhich extends below the strip b and isopposite a contact piece 1 fixed to the free end of the strip 22. Thestrips a and b are so designed that an increase of heat bends themtowards the base plate d. A lens 9 disposed between the electrodes 11.,z of the are 10 lamp and the strips a, 2; projects an image 7' of thelight are of the lamp, which uniformly covers the two strips a and bwhen the arc is in the prescribed position, both strips bending equallytowards the base plate (1 in such a manner that the contact e, f remainsopen. When the posi tive electrode h. is being consumed the image a isnow bent more strongly, and the strip a wanders towards the strip b (forinstance to the position represented by dash lines). The strip 17 20stretches accordingly, the contact e, I being closed rapidly. As aconsequence, the device for feeding the positive electrode is actuatedand the original condition reassumed. An alteration of the temperaturein the surrounding space causes the two strips to bend by equal amounts,so that, as desired, no closing of the contacts and .no consequentactuation of the feeding device will take place.

The device represented by Figures 4' and 5 diiters from the onedescribed above only by the iact that the transverse diameters of thebimetallic strips, which are designated k and l in this case, arestrongly inclined relatively to the direction of the radiation. 5

I claim:

A thermostat device for controlling the correct position of a movablesource oi radiation, especially the position of arc electrodes,comprising a support, two bimetallic strips sensitive to radia- 40 tionwhose one ends are fixed to the support, two contact pieces adapted tocontact each other, A each contact piece being fixed to one of the freeends of the two bimetallic strips, these contact pieces touching eachother only when the two bimetallic strips are not equally heated, anoptical system disposed between the source of radiation and the saidbimetallic strips and adapted to image the source of radiation on theseelements, the two strips lying next to each other in that direction intowhich the image of the source of light is being displaced when thesource of light is moving in a predetermined manner, the two stripshaving such positions that, when the source of radiation assumes itscorrect position;

the image of the source of radiation projected by the said-opticalsystem is uniformly divided over the two strips.

. CARL PRINZ.

